Focus problem on Nikkor 17-55 f/2.8

I recently purchased a Nikkor 17-55mm f/2.8 after reading all the great reviews about this lens. The reviews said the lens is tack sharp; however after doing a wedding, a model shoot and 2 engagement shoots with it, I'm concerned about the sharpness of the lens I have. I'm aware of the short depth of field issue when shooting at f/2.8, but I'm seeing the problem at other apertures as well. Up close it is very sharp, but at longer focal lengths, I'm not seeing sharp focus. I'm going to call Nikon, but thought I'd check here as well. Here are some photos from a recent shoot a model and I did for fun. Notice in the pictures of her against a wall that the focus may be slightly behind her, but at other times I'm not sure where the focus is. The lens is clean and I alway set my autofocus point on the face and on a near eye if I can get to one with a focus point.
http://www.timeseyephotography.com/brittany